This invention relates to a method and apparatus for making elastic diapers and, more particularly, for continuously applying adhesive to the moisture-impervious web of the disposable diaper in such a way that the ends of the elastic ribbons forming the leg bands are unadhered and can, therefore, "snap back" within the diaper. As such it is an improvement on co-owned Bradley and Merkatoris U.S. Pat. No. 4,585,507, the teachings of which are incorporated herein by this express reference.
The basic teaching for the manufacture of an elastic leg band diaper is found in U.S. Pat. No. 4,081,031 and consists of stretching the elastic ribbons, maintaining tension therein, and intermittently applying adhesive to selected portions of the elastic corresponding to the contractable leg portion of the diaper. The '507 patent was directed to apparatus which avoided the drawbacks of intermittent adhesive application. Other patents which were concerned with continuous adhesive application were U.S. Pat. Nos. 4,300,967 and 4,353,762 but which had other disadvantages as discussed in '507. In both of these cases, there was a "canceling out" of the activity of the adhesive.
Another expedient employed by the art to "unadhere" spaced portions of the leg band elastic is seen in U.S. Pat. No. 4,547,243 where, although the adhesive was applied continuously, the amount was reduced cyclically to achieve "snap back". But this again required special equipment to handle the modulation.
In contrast to the foregoing, the instant invention is inexpensive and reliable in both installation and operation. Essentially, it provides for continuously applying adhesive along a first longitudinally extending line and intermittently shifting the adhesive laterally to a second line. This is achieved advantageously by a pair of nozzles, i.e., air flow passages, which are angularly related and with a valve to control the air flow in at least one of the passages. The invention is particularly advantageous in connection with applying adhesive to a web about to be engaged by a non-rubber, i.e., elastomer ribbon. When such ribbons were used in the oscillating fork of '507, they tended to remain in V-folded condition. Other advantages of the invention may be seen in the ensuing specification .